Summary

Description

Limnodrilus hoffmeisteri is a small, thin worm about 20-35 mm in length. It has a simple conical shaped head, that lacks eyespots, and a long cylindrical body of numerous segments (55-95). The segments have on each side an upper and lower bundle of bristles (setae), that are able to move and are used for burrowing in sediment. The worm may appear red in colour, owing to the possession of the respiratory pigment haemoglobin. Like all other oligochaetes, the species is a hermaphrodite, with a complex reproductive system.

Recorded distribution in Britain and Ireland

Widely distributed around Britain and Ireland. The species is probably under recorded by surveys but reported in the upper Thames, Severn and Forth estuaries, and on the Norfolk coast east of Blyford.

Global distribution

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Habitat

It has a wide ecological range and inhabits cohesive muds in all types of waters including polluted, but it cannot tolerate oxygen deficiency. Although a freshwater species it is found further seaward than any other freshwater aquatic oligochaete species and is found in habitats likely to be exposed to very low salt levels, e.g. upper estuaries where interstitial salinity is less than 5 psu.

Depth range

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Identifying features

Small, thin worm, typically slightly longer than 2 cm in length.

Red in colour.

Eyespots absent.

Usually 7 setae per bundle on body segments.

Setae are all bifid (double-pointed), with the teeth of variable proportions

Testes in body segment X and male pore in segment XI.

Ovaries in body segment XI and spermatheca (sac-shaped invagination of body wall for receiving sperm during copulation) in segment X.

Additional information

Oligochaetes are segmented, bilaterally symmetrical, cylindrical worms, with tapering ends. They are very small, typically not much longer than 2 cm in length with a diameter of only a fraction of a millimetre. Typically each body segment possesses four bundles of setae (chitinous bristles projecting from the body). The setae vary considerably in size and shape, and between families, so are consequently used extensively in identification. Examination under a microscope and of internal anatomy is likely to be required for accurate identification and attention paid to the rather complex reproductive system. The number of gonads, the position of one gonad relative to the other, and the segments in which they occur are used to define the families. In the Tubificidae the form of the male duct is used to define genera.

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